Automatic telephone system



' Jar-1:12 192 C. E- LOMAX AUTOMATIC TELEPHONE SYSTEM Filed Sept. v, 1923 2 Sheets-Sheet 1 Inusn1ur $2155 E.Lumax HTTP.

2 Sheets-Sheet 2 Jan. 2 1926.

C. E. LOMAX AUTOMATIC TELEPHONE SY STEM Filed Sept. 7. 1923 P \N\ m L DJMI Ilaranns E.Ldmax ix Patented Jan. 12, 1926.

UNITED STATES 1,5 9,430 PATENT OFFICE.

CLARENCE E. LOMAX, OF CHICAGO, ILLINOIS. ASSIGNOR TO AUTOMATIC ELECTRIC COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Application filed September 7, 1923. Serial No. 661,343.

a citizen of the United States of America,- and a resident of Chicago, Cook County,

and State of Illinois, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the fol lowing is a specification.-

This invention relates in general to automatrc type similar to A, Fig. 1, and is matie telephone systems, but more particularly to small private installations, and its principal object is to provide means for the quick transmission of an important message to a selected group of telephones in the system. More specifically, the object of the invention is to provide means whereby a plurality of telephones, having individual lines, can be switched into one common group by dialling a specified number on a connector bank so that they can be signalled simultaneously and after answering be on a common talking circuit.

The means by which the foregoingand other objects are accomplished will be fully set forth hereinafter, reference being had to the accompanying drawings, of whieh 'Fig. 1 is a circuit diagram of the calling partys telephone A, individual line switch C, and connector H; while Fig. 2 is a circuit diagram of the group apparatus GA, called partys telephone A (having group service) and individual line switch C. 3

Referring to Fig. 1, the telephone A is of the usual automatic type and has, in

addition to the other well known instrumentalities, a calling device S for controlling the automatic switches. The line of telephone A when calling is given access through the medium of line switch C to a plurality of connector switches, one of which is.shown at H.

The individual lineswitches, of which the line switch C is typical, are mechanically of the rotary type of which thewipers have no normal position and move in a forward direction only.

The connector H is mechanically of the well known %vertical and rotary type of switch and has its bank contacts arranged in horizontal" rows or levels.

Referring. to Fig. 2, the group apparatus GA consists essentially of a. plurality of relays, a carbon generator lam L, and a ringing machine RM that delivers a distinctive ringing current to the group tele phones when they are called over the grouping circuit, together with suitable circuits for performing the necessary functions, as will be hereinafter pointed out. The apparatus to the left of the dead end leads is common to the group telephones, of which A" is one, while that to the right is individual.

The telephone A is of the usual autocapable of being rung by either of the ringing machines RM, Fig. 1, or RM, which deliver ringing currents of different interruptions.

The individual line switch C is similar to the line switch C of Fig. 1.

The utility of a telephone system of the above nature obtains, for example, in the case of a bank where an official desires to establish an immediate group. or conference connection with certain of his subordinates. The oflicials telephone, in this case, is as shown at A, while one of his subordinates telephones is as shown at A. The ofiicial may, by means of the connector H and group apparatus GA, establish connection with his subordinate A and those, subordinates grouped with him, by dialling their group number. There may also be more than one group in which case it would be necessary to make individual calls to transmit the same message to the other groups. I-Iaving given a brief description of the apparatus, the operation of same will now be explained in detail. Forthis purpose it will be assumed first that the party at telephone A, which is not one of the group telephones, desires to establish connection with the 1party at telephone A,which is one of the te ephones having group service, the

explanation being confined 'in the first instance to a regular connection. In order" to do this, the part at telephone A removes his receiver and t en dials the number of the desired party.

When the receiver is removed at telephone A, line relay 14 energizes over line conduc-- tors 11 and 12. Upon energizing, line relay 1 places ground on private normal conduct-or 30 at armature 19, thereby making the calling line busy, and closes a circuit for switching relay 13 and stepping magnet 15 in series. As a further result of the energization of line relay 14, it connects test wiper 22 to the of switching relay 13 and stepping magnet 15 at armature 20.

In case the trunk upon which the wipers of the line switchare standing is idle, switching relay 13 energizes immediately. Assuming the trunk to be busy, however, switching relay 13 is short circuited by ground encountered on the busy test contact by test wiper 22 and does not energize, and the Wipers are rotated step by step by the buzzerlike action of stepping magnet 15, which operates through test wiper 22. When an idle trunk is reached, which trunk it will be assumed is the one terminating in bank contacts 24, 25 and 26, switching relay 13, being no longer short circuitedg-energizes in series with stepping magnet 15. ping magnet 15, however, does not energize at this time on account of the high resistance of switching relay 13. Switching relay 13, upon energizing, opens a point in the test circuit and; prepares the holding circuit at armature 17, and at armatures 16 and 18 disconnects line conductors 11 and 12 from the winding of line relay 14 and ground, and extends them by way of wipers 21 and 23, bank contacts 24 and 26, and the associated line conductors to the windings of line relay 33 of the connector H.

Line relay 33 now energizes over the calling partys loop and closes at armature 50 a circuit for release relay 34. Upon energizing, release relay 34 opens a point in the circuit of release magnet and prepares a circuit for vertical magnet 71 at armature 53, places ground upon armature 58 of busy relay 38 at armature 52, and at armature 51 places ground on the release trunk conductor 28, thereby closing the usual holding circuit for switching relay 13 of the line switch C before the slow acting relay 14 has had time to deenergize.

The calling device at telephone A may now be operated in accordance with the first digit in the desired number. As a result a corresponding number of terruptions are produced in the circuit of ine relay 33 of connector H. Each time linefrelay 33 deenergizes in response to one of these interruptions, it sends an impulse of current to vertical magnet 71, the first impulse of current being sent over the following circuit: from ground by way of armature 50 and its resting contact, armature 53 and its working contact, restin contact of off normal spring 69 and sai spring, relay 35, and vertical magnet 71 to grounded battery. By the operation of vertical magnet 71, the wipers 81, 82 and 83 are raised step by step until they stand opposite the correct level of bank contacts in which the line oftelephone A terminates. Relay 35 is energized in series with vertical magnet 71 and, being slow acting, retains its armature 54 attracted throughout the vertical movement, thereby movement, slow acting relay 35, upon deenergizing, shifts the impulse circuit from the vertical to the rotary magnet at armature 54.

The calling party now operates his calling device in accordance with the next and last digit in the desired number, whereupon a corresponding number of interruptions are produced in the circuit of line relay 33 of the connector H. Each time line relay 33 deenergizes in response to one of these interruptions, it sends an impulse of current to rotary magnet 72 by way of the following circuit: from ground by way ,of armature 50 and its resting contact, armature 53 and its working contact, normally open contacts controlled by oft normal spring 69, armature 54 and its resting contact, resting contact of armature 59 and said armature, armature 66 and its resting contact, and rotary magnet 72 to grounded battery. By the operation of rotary magnet 72. the, wipers 81, 82 and 83 are rotated step by step until they come to rest upon the correct set of bank contacts in the correct level, which set coinprises bank contacts 84, 86 and 88. Relay 39 is energized in multiple with rotary magnet 72 and, being slow acting, retains its armature attracted throughout the rotary movement. Upon energizing, relay 39 disconnects test wiper 82 from the upper windingof switching relay 40 and connects it to busy relay 38 at armature 61, and at armature 62 places a shunt around armature 59 and its resting contact so as to render its own circuit and that of stepping magnet 72 independent of armature 59 which armature is attracted by busy relay 38 in case test wiper 82 is rotated over grounded test contacts.

It will be assumed first that the line of telephone A is busy when called. That being the case, test contact 86'is grounded and busy relay 38 is accordingly energized when test wiper 82 arrives upon the test contact of the called line. That being the case, relay 39, upon deenergizing at the end of the rotary movement, disconnects itseli and rotary magnet 72 from the impulse circuit at armature 62 (armature 59 having been operated) and at armature 61 opens the initial circuit of and completes a locking circuit for busy relay 38, the locking circuit being as follows: from ground by way of the working contact of armature 52 of release relay 34 and said armature, armature 58 and its working contact, normally closed contacts controlled by armature 61, and relay 38 to grounded battery. As a further result of the energization of busy relay 38, it connects a lead from the busy signalling hears at this time the tone produced by said inbefore described.

busy machine B and is informed thereby that he cannot obtain the desired connection for the time being. Upon hearing-this busy tone, the calling party replaces his receiver, whereupon the entire connection is released in a manner to'be hereinafter described.

It will be assumed now that the line of telephone A is idle when called as here- That being the case, busy relay 38-is not energized at theend of the rotary movement and slow acting relay 39, upon deenergizing, closes a circuit for switching relay 40 in series with switching relay 213 of the line switch C of the called line as follows from ground by we of the working contact of armature 52 0 release relay 34 and said armature, armature 58 and its resting contact, upper winding of switching relay 40, resting contact of armature 61 and said armature, test wiper 82, test contact 86, private normal conductor 90, switclr ing relay 213, and stepping magnet 215 to grounded battery. Switching relays 40 and 213 energize in series over this circuit. Stepping magnet 215, however, does not energize at this time on account of the high resistance of switching relay 213. Switching relay 213, upon energizing, clears the called line of its normal battery and ground connections but owing to the usual mechanical inter-locking device (not shown) between its armature-and the armature of line relay 214, the armature of switching relay 213 is operated only about half Way and consequently the switch wipers are not connected up.

In the connector H, switching relay 40, upon energizing, closes a locking circuit for itself at its lightly adjusted armature 65, which armature is adjusted to make contact with its working contact before the other armatures of the relay are operated; disconnects rotary magnet 72 and relay 39 from the impulse circuit at armature 66 so as torender ineffective any further operation of the calling partys calling device; places direct ground upon test wiper 82 at armature 64; and at armatures 63 and 67 connects up line wipers 81 and 83. Ringing current is now projected out over the called line intermittently by the ringing machine RM. This ringing current returns by way of the bridged bell and condenser at the called telephone, and the upper winding of ring cut off relay 37. Owing 'to the fact that rlnging current is passing throughthe upper wmdmg of ring cut off relay 37 an alternating E.,M. F. isinduced in the lower winding thereof, thereby sending a ringing tone back to the calling party by way of the lowe'i""'*winding of back bridge impedance 36 and the lower heav'y talking conductor.

When the called party responds to the ringing of his bell by removing his receiver, a direct current bridge is placed across the conductors of the called line. Ring cut off relay 37, upon energizing over the called line, closes a locking circuit for itself and places ground on the lower winding of the back bridge impedance 36 at its lightly adjusted armature 56, which armature is adjusted to come into engagement with its working contact before the other armatures have moved, and at armatures and 57 dis connects its own upper winding and the generator lead and connects the called line with the upper and lower windings of back bridge impedance The calling and called parties may now converse with each other in the usual man ner, the talking circuits being outlined by heavy conductors, and after the conversation is terminated the calling and called parties replace their receivers.

When the receiver is replaced at telephone A, thecircuit of back bridge impedance 36 is opened, and when the receiver'is replaced at the calling telephone A, the circuit of the line relay 33 of the connector H is opened. Line relay 33, upon deenergizing, opens the circuit of release relay 34 and prepares a circuit for release magnet at armature 50. Release relay 34, upon deen ergizing, removes ground from armature 58 of busy relay 38 at armature 52, and at armature 51 removes ground from release trunk conductor 28,-whereupon ring cut off relay 37 switching relay -40, and switching relay 13 of line switch C deenergize. When this occurs the line switch C is restored to normal condition in the usual manner. The deenergization of switching relay 40 disconnects the line wipers at its upper and lower armatures, and rempves the busy potential from the test contact of the called line at armature 64. As a further result of closes at armature 53 a circuit for release magnet 70 by way of off normal contacts 68. In response to'the energizatlon of release -magnet 70, the shaft and wipers of the connector H are restored to normal position in the usual manner, the circuit of release magnet 70 being opened at off normal contacts 68 by the switch shaft when the latter reaches normal position. The entire connection is now released, the busy potential is removed from the test contacts of the calling and called lines, and the common equipment used to extend the connection is restored to common use.

v It will be assumed nowthat an ofiicial of the bank, whose telephone is A, learns of a contemplated attempt to cash a worthless check and desires to establish quick connection with the common group telephones assigned to the paying tellers, one of which the deenergization of release relay 34, it

is shown at A. In order to do this, the party at telephone A removes his receiver and then dials the specified number.

\Vhen the receiver is removed at telephone A, the line switch C operates in the hereinbefore described manner to select an idle connector, which connector it will be assumed is the one shown as H. The line relay 33 and release relay. 34 of the connector H energize and prepare the switch for operation in the usual well known manner.

lVhen the calling party at telephone A operates his calling device in accordance with the common group telephone number the connector H operates in the hereinbefore described manner to raise its wipers 81, 82 and 83 opposite the correct level of bank contacts and then rotates them in to the correct contacts, in this case indicated as 85, 87 and. 89.

When wiper 82, of connector H, comes to rest on bank contact 87 the following circuit is closed: from ground by way of the working contact of armature .32 of release relay 34 and said armature, armature 58 and its resting contact, upper winding of switching relay 4.0, resting contact of arn'iature 61 and said armature, wiper 82, contact 87, private normal conductor 91, and relay 101 to grounded battery. Relays 40 and 101 energize in series over this circuit. Switching relay 40, upon energizing, closes a looking circuit for itself at armature 65, disconnects rotary magnet 72 and relay 39 at armature 66, places direct ground upon wiper 82 at armature 64, and at armatures 63 and 67 connects up line wipers 81 and 83, as described in detail hereinbetore.

lVhen the line is closed at armatures 63 and 67 a circuit is closed as follows direct ground or grounded generator, depending upon the position of the ringing machine RM at the time the line is closed, by way of armature 75, resting contact at armature 57 and said armature, armature 67 and its working contact, wiper 83, contact 89, armature 113 and its resting contact, contact 85, wiper 81, working contact of armature 63 and said armature, armature 55 and its resting contact, and the upper winding of ring cut off relay 37 to grounded battery. Ring cut off relay 37, upon energizing, closes a locking circuit for itself, places ground on the lower winding of back bridge impedance 36, and disconnects its own upper winding and the generator lead and connects the common line leading to the group telephone with the upper and lower windings of back bridge impedance 36, as described in detail hereinbefore.

In the group apparatus GA, relay 101, upon energizing, opens thecircuit of relay 102 and closes a circuit for group busy relay 103 at armature 111. Relay 102 being slow acting, holds its armature 112 attracted sufliciently long to permit group busy relay 103 to become energized by Way of grounded armature 111 and its working contact, and then deenergizes, opening the circuit of relay 103 at said armature 112, and removing the short and connecting the talking conductor through at armature 113. Group busy relay 103, upon energizing, closes circuits at its armatures for the group apparatus GA switching relays of all lines having group service. For example, at armature 114 a circuit is closed for switch relay 107 from ground, .working contact of armature 114 and said armature, relay 107 to grounded battery. Switching relay 107, upon energizing, closes at armature 123 a locking circuit for itself by way of ground at armature 116; places ground upon private normal conductor 90 at armature 122, thereby making the line of station A busy to the connectors; disconnects, at armatures 121 and 124, the said line from its individual line switch C and connects it to the group apparatus GA. In a like manner all other lines in the group are individually made busy, are disconnected from their individual like switches, and are connected to the group apparatus. Ringing current interrupted difi'erently from that used for normal service is now projected out over the lines in the group intermittently by the ringing machine RM. For example, this ringing current ,is projected out over the line of telephone A as follows: from ringing machine RM, resting contact of armature 11 7 and said armature, series holding relay 106, working contact of armature 124 and said armature, line conductor 212, telephone A, line conduetor 211, armature 121 and its working contact, armature 115 and its resting contact, and lamp L to grounded battery. Relay 106 will not energize in series with they condenser at telephone A.

When the called party at station A. responds to the ringing of his hell by removing his receiver, a direct current bridge is placed across the conductors of the called line to replace the bell and condenser. Relay 106 now energizes, closes at armature 119 a multiple locking circuit for relay 107 by way of armature 123 and its working contact; closes at armature 120 a circuit for ring out off relay 105. Relay 105, upon energizing,

opens at armatures and 117 the ringing circuit, the latter armature being adjusted to operate after armatures 115 and 118 to insure the continuous holding up of relay 106; and closes at armatures 115 and 118 the talking circuit which includes the high im- 125 pedance 104. In like manner all other lines in the group are disconnected from the ringing source and connected to the common talking circuit. It will be readily seen that the answering of any telephone in the common grou will not stop the ringing current to those telephones which have not answered,

' due to the fact that they have individual ring out off relays.

, Thecalling party may now converse with the parties in the group to give them any necessary instructions, etc., after which the connection is terminated by the calling and called parties replacing their receivers.

When the receiver is replaced at telephone A the direct currentbridge across the conductors isreplaced by the bell and condenser. opens at armature 119 the circuit of relay 107 and opens at armature 120 the circuit of relay 105. Relay 107, upon deenergizing, removes busy ground from private normal conductor 90 at armature 122; disconnects at armatures 121 and 124., the line of station A from the common group talking circuit and connects it to its-individual line switch C Relay 105, upon 'deenergizing, repares at armature 116 a locking circuit or relay 107; further disconnects at armaturcs 115 and Y118 the talking circuit; and prepares at armatures 115 and 117- the ringin circuit. In like manner all other lines in t e group are disconnected from the common group talking circuit and connected to their individual line switches. I

When the receiver is replaced at telephone A, the line switch C and connector H are restored to common use in the hereinbefore described manner. When ground is removed from wiper 82 at armature 64 of relay the circuit of relay 101 is opened. Relay 101, upon deenergizing, closes at armature 111 the circuit of relay 102. Relay 102, u

on energizing, prepares at armature 112 t e circuit of relay 113 a short across'th'e talking conductors. Thus the common equipment of the group apparatus GA is also restored to norma Due to each telephone line in the common group having'a series holding relay, and a switching relay the releasing of any telephone from the common group circuit is under its own control at all times; also the rotation of the individual line switches of the group lines, in hunting for an idle trunk, is prevented, as would be the case if the releasing of the group lines were under control of the person who established the group and that person hung up first.

In order to explain the operation of the system further it will be assumed that the bank ofiicials telephoneis one of the common group telephones, in this case A, and that he desires to establish quick connection with the other common group telephones. In order to do this he removes his receiver and then dials the specified number.

When the receiver is removed at telephone A, the line switch C operates in the manner hereinbefore described for line switch C to Select an idle connector, which connector Relay 106, now deenergizes,

103; and closes at armature it will be assumed'is the same one as selected by line switch C, i. e., the one shown as H. The line relay and release relay 34 of the connector H energize and prepare the switch'for operation ;in the usual well known manner.

When the bank official at telephone A operates his calling device in accordance with the common group telephone number the connector H operates in the hereinbe fore described manner to raise its wipers 81, 82 and 83 opposite the correct level of bank contacts and then rotates them in to the-correct contacts, indicated, as before, as 255, 87 and 89. The connector then operates, as before, to connect up the line wipers and the ringing source, and then disconnects the ringing source and connects the talking conductors through. 1

The group apparatus (JrA operates in the hereinbefore described manner to remove the short from across the talking conductors,

'busy the called lines, disconnect the called lines from their individual line switches and connect them to the group apparatus, project ringing current out over the called lines, and when the parties answer disconnect the ringing source and connect the talking conductors through; In the case of telephone A where a connection .is set up via line switch C, seized connector H, and group. apparatus GA, it will be noted that this line is transferred from its individual dual line switch C to the group apparatus by the switching relay 107 regardless of the fact that it is in use at the time. When the line is transferred the line switch 0, the seized connector H, and relays 101 and 102 of group apparatus GA restore to normal, as previously described, leaving the common ringing source RM connected to the group telephones. The receiver being ofi the hook at telephone A at this time, the series holding relay 105 immediately energizes, whereupon ring cut oil relay 1105 energizes to disconnect the line from the common ringing source and connect it to the common talking circuit.

The calling party at telephone A may now converse with the other parties 'in the common group in the usual manner and after' the conversation is terminated the calling and called parties replace their receivers. When the receivers are replaced busy 4 round is removed from the private norma s, and the lines are individually disconnected from the common group talking circuit and connected to their individual line switches, as has already been described in detail. y

Attention is directed to the fact that the party at group telephone A, due to the line conductors terminating in the individual line switch C, can call the other group telephones individually as well as the tele- Having described my invention, what I,

consider to be new and desire to have protected by Letters Patent will be pointed out in the appended claims.

What I claim is:

1. In a telephone system, a calling station, a plurality of called stations, automatic switching equipment controlled from said calling station for connecting with any of said called stations individual y and for signalling the subscribers thereat, group apparatus co-operating with said switching equipment to enable the party at said calling station to set up a conference connection including all said called stations, and means for automatically signalling the called stations in a different characteristic manner in the latter case to notify the subscribers that they are being called for a conference.

2. In a telephone system, a plurality of stations having individual lines, a common ringing circuit, a common talking circuit, means whereby a predetermined number of said stations can be switched to said common ringing circuit and rung in a characteristic manner therefrom, and means whereby any station in said common ring-' ing circuit can switch its line to said common talking circuit without interfering with the ringing of the stations which have not answered.

3. In a telephone system, a plurality of telephones having individual lines, a common ringing-circuit, a common talking circuit, means whereby certain of said telephones can be connected to said common ringing circuit, means whereby the telephones connected to said common ringing circuit can be switched individually to said common talking circuit, and means whereby 'the release of any telephone from said common talking circuit is under its own control at all times.

at. In a telephone system, a plurality of stations having individual lines some of which are arranged for group service, a common ringing circuit, a common talking circuit, means whereby said common ringing circuit can be established by any station, in said system, and means whereby said common talking circuit is established through the individual answering of said group stations, and means whereby any subscriber in the group can release and establish a separate connection without affecting the group call.

5. In a telephone system, a plurality of individual lines a limited number of which are wired and equipped for conference group service, a common ringing circuit, a common talking circuit, means whereby any tele hone in said system can establish a conference group, and means whereby telephones having group service can be switched directly from said common ringing circuit to said common talking circuit in case the receiver is off when the group is being established.

6. In a telephone system, a plurality of telephones having individual lines some of which are arranged so as to be connected in a group, a group ringing circuit, a group talking circuit, means whereby said group telephones can be connected to said group ringing circuit whether they are busy or not, means whereby any telephone on said group ringing circuit can have its line switched to said group talking circuit without interfering with the ringing of the telephones which have not answered, and means whereby any of said group telephones can be switched back to said group talking circuit in case they disconnect prematurely without disturbing the telephones which have not disconnected.

7. In a telephone system, a plurality of telephones having individual lines some of which are arranged for group service, a group talking circuit, means whereby said telephones arranged for group service can be disconnected individually from said group talking circuit, and means whereby said disconnected group service telephones can be reconnected to said group talking circuit without disturbing the telephones that have not disconnected.

8. In a telephone system, a plurality of individual lines, a limited number of which are wired and equipped for conference group service, a common ringing circuit, a

common talking circuit, means whereby any telephone in said system can establish a conference group connection, said common ringing circuit ringing the called lines simultaneously, means operable'when a called line answers for switching that line to the common talking circuit, and means whereby the calling line can disconnect from the group without affecting the lines on the common talking circuit.

In witness whereof, I hereiuito subscribe my name this 4th day of September, A. 1).,

CLARENCE E. LOMAX. 

